What are the “fairy circles”, the formations found in arid regions that still arouse the curiosity of scientists?

Members of the Himba tribe in Namibia have said for generations that the powerful breath of the dragon left marks on the ground.

These are semicircular marks, where vegetation has not grown back. All that remains is bare earth, surrounded by grasses common to the arid lands of southwest Africa.

In the 1970s, South African ecologist Ken Tinley noticed that these plots of land were similar to the famous rings formed by mushrooms in Europe. He gave the formations the name “imaginary circles.”

Tinley believes they may have been created by termites. But to this day, these land formations remain a mystery. Scientists have debated it for many years and have yet to reach an agreement about its origin.

But the new research adds a new element to the discussion. Fairy circles are not only found in southwest Africa and northwest Australia, as was thought until now.

He explains to BBC News Mundo: “From space, with the help of an artificial intelligence model, we have found hundreds of places in arid regions of the world that have not been described before, with vegetation patterns similar to imaginary circles.” BBC Spanish-language service) Scientist Emilio Gerado, from the University of Alicante, in Spain.

The study revealed that imaginary circles exist in at least 15 countries on three continents.

His research did not seek to reveal the origin of these formations. But the data provided can help find the answer.

Discussion of the years

Despite their name, fairy circles are often hexagonal formations in the ground. Vegetation doesn’t grow inside it, but around it – at least most of the time.

Following Tinley’s research in the 1970s, scientific discussions about the origins of chimeric circuits moved toward two main theories.

One of them was introduced in 2013 by German biologist Norbert Jürgens. After a decade of research, he determined that the imaginary circles are formed by subterranean termites.

According to Jurgens, these insects feed on plant roots that begin to grow after rainfall, which generates accumulations of water underground and allows termites to survive.

“Termites are social insects that dominate their territories, where water and food are available. Colonies defend their territory from neighbors, sometimes very aggressively,” Jurgens explained to BBC News Mundo in 2016.

The German biologist stated that imaginary circles constitute a “system of competition between colonies.” He is “pretty confident” in his theory, which he says has been confirmed by several of his colleagues.

Almost in parallel, German ecologist Stefan Getzen and Israeli physicist Ehud Meron collaborated to conduct research on fairy circles in Australia. They argued that its formation is explained by the theory of self-regulation.

Meron explained to BBC News Mundo, after publishing his study in 2016, that nature is facing water scarcity with this phenomenon.

The researcher believes that “the surrounding plants, organized in the form of circles, benefit from an additional source of water, as rain in areas of terrain finds its way through various water transport mechanisms.”

“In Australia, this mechanism involves the flow of water over the ground, while in Namibia it is about spreading stored water,” Miron said.

In doing so, Miron and Getzen ignored Jürgens’ theory because, according to them, there were no termites in the fairy circles studied in northwestern Australia. Jürgens disputed this finding, saying that his colleagues had not dug deep enough to find the insects.

What does the new research say?

The research conducted by Emilio Girado’s team did not seek to find reasons for the formation of chimeric circles. They created a map of where these formations are located.

The scientist explained that they used two artificial intelligence models and found hundreds of places with imaginary circles in the arid regions of the world (which represent 41% of the Earth’s surface).

They analyzed several factors, such as climate, soil and environmental factors. They concluded that in places where these variables are stable, fairy circles exist, especially where the soil is sandy.

“We analyzed hundreds of thousands of images and discovered hundreds of plant patterns matching imaginary circles in arid regions of the world,” explains Gerado. “This process took just over a month on a high-speed computer with four GPUs [GPUs, na sigla em inglês]”.

With the help of two artificial intelligence models, they searched through 600,000 satellite images from global mapping services, such as Google Earth, Bing Maps and Mapbox, looking for images of the terrain at a higher resolution.

With this, they were able to obtain clearer images of the barren spots on Earth where fairy circles exist.

As a result, researchers found fairy circles at 263 points on the planet, located in 15 countries in Africa, Asia and Oceania.

These regions include the Sahel region of Africa, Western Sahara, the Horn of Africa, Madagascar, southwest Asia, and central Australia.

When asked whether his research provides any explanation about the origin of these patterns, the Spanish scientist replied that the unknown remains. It neither ignores nor defends hypotheses that have already been advanced.

What is certain is that this is a wasteland phenomenon, as it would be almost impossible to observe in other areas.

“In theory, in places where there is greater rainfall, the circuits will close,” explains Gerado.